1. Field of the Invention
This application relates generally to an improved radar processing method and system, and more specifically to radar imaging and target identification, and in particular to a method and apparatus for improving the representation of targets within radar images.
2. Description of Related Art
Radar is the primary airspace sensor for ground-based, marine and airborne surveillance and monitoring applications. Its use within both commercial and military environments is widely known, and to date it remains the most effective technique for identifying targets within an area of interest.
Conventional radar display systems have historically been based on cylindrical cathode ray tube (CRT) arrangements, in which a phosphor screen is excited by a sweeping beam that is synchronised with the rotation of the radar antenna. Any target objects within the monitored area give rise to a return (i.e. reflected) radio signal that appears as a ‘blip’ (e.g. a bright spot/area) on the radar image display. This kind of display is usually referred to as a plan position indicator (PPI), which functions as a range and azimuth map centered on a polar coordinate system. Since the phosphor typically has a long persistence, a target signal will remain visible for several rotations or scans of the sweeping beam. Thus, moving targets are found to leave a visible trail of decayed images on the image display. In this way, the position and velocity of a target can be reliably monitored, allowing an operator to determine the direction in which a target is heading.
Despite the large number of CRT radar display systems that remain in existence, more recent implementations have begun to make use of computer-based technologies and software in order to replace and/or upgrade the more historical image displays. For instance, many modern radar display systems have been implemented within computer workstation environments, in which a radar signal feed is passed to the workstation for display to an operator as a series of real-time radar images. The images are typically displayed via the workstation's monitor, which may be a conventional VDU, TFT or LCD style display device.
In order to successfully implement a radar display system within a workstation environment a large degree of data processing is typically required. Most radar signal feeds are analogue in nature, so it is usual to convert the feed to digital form via an analogue-to-digital converter. The digital radar data is then conventionally processed via a ‘Radar Scan Converter’ (RSC) that converts the range and azimuth data from a polar coordinate system into a dataset based on rectangular (i.e. Cartesian) coordinates for real-time display on the workstation's monitor.
However, a potential drawback of many such implementations is that the amount of processing power required to perform the digitization and/or conversion is relatively high, which consequently places significant demands on the workstation's CPU and associated memory. In some cases, the CPU demands may be so great that this introduces a significant delay into the image processing, such that the displayed image lags behind the radar signal feed, which is obviously undesirable within most radar applications. To a limited degree, the art has addressed this problem by attempting to ‘load-balance’ the processing requirements between the CPU and the processing elements on the workstation's graphics card. However, in nearly all cases, such implementations have fallen significantly short of removing the processing burden from the CPU. Therefore, to date, most of the known computer-based implementations of radar display systems are highly CPU intensive.
Computer-based implementations offer significant flexibility and scalability in controlling the display of radar images. Many of the known workstation implementations provide radar images which offer considerably better rendered detail than conventional CRT displays. However, it is usually the case that existing techniques used to process the radar images generally do not make best use of the available data and, in particular, are not especially suited to mitigate against the effects of noise within the radar images. Therefore, the representation of targets within a displayed image may not match those that are theoretically possible given the power and/or resolution of the radar display system.
The present invention seeks to provide a much improved and less CPU intensive method for displaying radar images, so as to enhance the identification and representation of targets by processing the images to extract the maximum amount of information from the radar signal and minimize, or substantially eliminate, sources of background noise.